Natural gas has been used as an alternative fuel for internal combustion engines in mobile machines. Because natural gas has a lower volumetric energy density than traditional fuels, such as diesel and gasoline, mobile machines generally utilize liquefied natural gas (“LNG”). At atmospheric pressures, natural gas must be chilled to below about −160° C. to remain in liquid form. Mobile machines utilizing LNG as a fuel, store the LNG in insulated tanks. Because these tanks are not perfect insulators, heat enters the tanks, causing some of the LNG to boil (“boil-off”). The boil-off increases the pressure of the tanks, and can cause excessive stress to the tanks if not removed. Traditional LNG systems vent the boil-off (composed mostly of methane) directly to the atmosphere. However, because methane is a greenhouse gas, government regulations are soon expected to prohibit the direct venting of boil-off to the atmosphere.
One method of handling boil-off from an LNG tank is described in U.S. Patent Publication No. 2008/0053349 (“the '349 publication”) of O'Connor that published on Mar. 6, 2008. The '349 publication describes a marine vessel having a tank for storing LNG. The '349 publication delivers boil-off gas from the tank to a combustion section via a gas inlet. Combustion air is also directed to the combustion section and the resulting air-gas mixture is ignited. This system effectively converts the boil-off to carbon dioxide and water, which are less harmful to the environment.
Although the system of the '349 publication may be capable of preventing boil-off from directly venting to the atmosphere, it may be wasteful. Specifically, because the system of the '349 publication only combusts the boil-off, energy associated with the boil-off is lost from the system as heat and exhaust.
The energy recovery system of the present disclosure solve one or more of the problems set forth above and/or other problems with existing technologies.